Holder devices of the type mentioned by way of introduction are previously known in this Art and may, for example, be intended for the transport of bicycles on a vehicle roof.
Such prior art holder devices have, for instance, been secured to a roof rack or the like extending across the vehicle roof, by means of U-shaped threaded stirrups which are positioned about the rack and are screwed in place in the holder device. In such instance, use may be made of conventional nuts, in which even the holder device runs the risk of being stolen, together with the load carried thereon. Alternatively however, use may also be made of hand nuts which are lockable by means of a cylinder lock. Since the roof rack frame is also lockable on the vehicle by means of a cylinder lock and, as a rule, also the load itself in the holder device by means of a further cylinder lock, it will be readily appreciated that there is a considerable risk of confusing the various keys involved. Furthermore, the risk of losing these keys cannot be discounted.